Modern Vespa

My PX starter Motor has never worked since I fitted my Pinasco Alu 177 last year.
The battery is fine and has the required 12 volts. I have even replaced the battery for a new one but still the same symptoms.
Starter Motor is able to turn the motor over only a couple of times and then stops.

Any idea what I can check further?
Im not sure if the Starter motors can be serviced in any way or serviced?

Thanks
Robbie

A good battery should have closer to 12.6 volts, not 12. Only having 12 volts might not be enough to keep the motor spinning. Double check your voltage with a electrical tester is what I would check first. Then I'd look at the relay for the starter, or the wires that are coming and going to and from the relay. After that, check the starter for corrosion.

Check the voltage when you are trying to start. Also what is the actual voltage as stating 12v doesn't tell you anything. Check the ground cable for any corrosion or damage. You can take the starter off and check the brushes and the condition of the internals. The new kit might have too much compression to allow the started to turn over.

If it is similar with Polini, the cylinder bottom could interfere with the starter ring. According to Polini manual it is saying that you need to cut the bottom of the cylinder because it interferes with the starter ring on electric starter models. Please find at the attachment.

Additionaly, the clutch sensor cable on the left hand Side could be broken.

Did you cut the bottom fin off?
Check the studs have not screwed in too far.

Both these can cause interference with the starter motor teeth

If the flywheel spins a couple of complete rotations with no funny noise, it should not be locked up. The following supposes it runs after kick starting. Is it more hard to kick due to higher compression after the kit? Did it always spin and start well, before the kit? Original crank and flywheel? Do wires get warm/hot?

Remove the spark plug and see how well it spins without compression. It should, and if it does, let it spin for a while to possibly clean brushes/commutator or see if it could be what has already been posted.

Hooking a large enough temporary wire directly from the battery to the starter can help narrow the problem down to relay/wiring/connection problems as long as the grounding is good. Corroded/pitted relay contacts/connections are common.

If the battery is unable to provide sufficient starting amps, using jumper cables from another stronger battery might help diagnose, but could heat things up and possibly cause damage if there is an electrical or jamming problem. Use caution.

If jumper cables work, with no noticed problems, you might just need a higher capacity battery. To work properly against a harder to spin engine will require more battery amps. AGM mount any position are my favorites. I use these type 9 amp hour batteries to start engines up to 50 hp, even after adapting .25" female terminal ends. Installed vertically on a P.

http://www.ebay.com/itm/192011783141?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Brushes, commutator, and shaft bushings. Shaft bushing wear on either end of a starter has been my most common starter problem. Rotating assembly must be centered and easy to spin (lubricated bushings).

Thanks for all the feedback.

So this morning I checked the voltage of the battery and its 12.4 volts.
The problem is when I try and run the starter motor the voltage in the battery goes down to about 4.5 volts (measuring with a voltmeter while trying to turn-over the engine).
I also replaced the starter relay with one thats working and still the same symptoms, short turn of the flywheel and then nothing more.
The Pinasco does have a lot of compression as it has the VRH Pinasco high compression head. As recommended I will also try and turn the motor over with no spark plug to see if its the compression thats the issue.
I rebuilt the Vespa totally so never had the motor running so I cant be sure if the starter ever worked properly or not.
The flywheel turns no problem if kick-started so its not the flywheel rubbing anywhere.
Maybe I should also go with a 12Volt 9 amp battery, it would only be an advantage?

Thanks Guys

Maybe your starter has worn out brushes and hasn't got the "horsepower" anymore to turn the engine due to the high compression...

So resting volts = 12.4, good enough (new is 12.6). Cranking volts = 4.5. Not good as it should not be below 10.3-5. Starter, wiring or battery is wonky. If the battery is older than two years, I would suspect it first. Most auto part places can test it for you. If you jumping it off a known good car battery and it's still a no go, then look to your wiring. You could easily bench test your starter or leave it on the bike and run the jump wires directly to it. Lastly, I don't know, but I'm guessing there may be a neutral safety switch that could be causing the problem? I'm glad these scoots kick start so easily. Good luck.

12.4v is not that great, as it's about 70-80% charged. A good charged resting voltage should be 12.6v to 12.7v.

Have you let this battery sit without a charger on it for any period of time? Or low water? Realisticly voltage does not tell you how healthy a battery is.

The battery is at least 4 years old, so probably a good idea to replace it.
I will order a new one and see how that goes.

Thanks for all the advice..

Even you use the scoot fairly often and/or keep it hooked up to a battery tender, you should see at least three good years from a battery. If not, the time gets shortened considerably.